Potassium inwardly-rectifying channel, subfamily J, member 16 (KCNJ16) is a human gene encoding the Kir5.1 protein. Potassium channels are present in most mammalian cells, where they participate in a wide range of physiologic responses. Kir5.1 is an integral membrane protein and inward-rectifier type potassium channel. Inward rectifier potassium channels are characterized by a greater tendency to allow potassium to flow into the cell rather than out of it. Their voltage dependence is regulated by the concentration of extracellular potassium; as external potassium is raised, the voltage range of the channel opening shifts to more positive voltages. The inward rectification is mainly due to the blockage of outward current by internal magnesium. KCNJ16 may be involved in the regulation of fluid and pH balance. In the kidney, together with KCNJ10, mediates basolateral K+ recycling in distal tubules; this process is critical for Na+ reabsorption at the tubules.